What’s Up? March 2025

In this month's What’s Up, astronomer Rosie talks us through March’s highlights.
I don’t know about you, but I’m sure glad to see the first daffodils growing. It was a long winter! Spring and sunshine are creeping in and it turns out, March is jam packed with celestial and astronomical events! Let’s dive in.

Spring Equinox

Thursday 20^th of March marks the first day of Spring in the Northern Hemisphere! It’s the time where the Sun sits right above the Earth’s equator meaning both hemispheres receive approximately the same amount day light. In the north, we call it the spring or vernal equinox, as the days are starting to get longer than the nights again.

Image: On the equinox, the Sun sits right above the equator. Credit: timeanddate.com

Constellations

Our beloved winter constellations such as Orion, Canis Major and Taurus are still nicely visible in the night sky in the early evening. But as the night gets late, we are seeing our spring favourites out: Cancer (though always a tricky one to see because it’s so faint), Leo, Virgo, and personally for me the constellation that means winter is over - Boötes.

Boötes contains the orange giant Arcturus, the fourth brightest star in the night sky. For many of us at the observatory, seeing Arcturus means spring is officially here.

Image: Boötes, the herdsman in Greek mythology. Arcturus is the brightest star in the constellation, and is an orange giant only 37 light years away (very close!) Credit: Stellarium

Planets

The planetary parade that graced our skies in February will be starting to dwindle. Saturn will be gone by the end of February, and Venus and Mercury will stick around for a few days at the beginning of March but then sadly leave. Jupiter and Mars however are stubborn and will still be visible for the whole month! Uranus as well to those with a telescope.

Mercury, the little rascal, is always the hardest of the naked-eye planets to see. It’s the closest to the Sun so there’s such a short window either before sunset or sunrise to capture it. However, leading up to the 8^th of March it will be at its greatest elongation east, meaning it will be the farthest east from the Sun from our perspective.

This is a fantastic chance to try and spot Mercury if you’ve never seen the planet before. If there’s a clear evening during the first week of March, go outside and find the lowest horizon possible towards the west. Start looking just after sunset at about 18:00 UTC. You will see Venus, shining like a diamond, but you want to look below Venus very close to the horizon. As the days go on Mercury will also become dimmer, so I’d recommend the 3^rd - 7^th of March if possible.

Image: The messenger god moves swiftly. Trying to spot Mercury is a tricky business because it moves so fast and stays close to the Sun. Simulation of the evening sky on the 4^th of March at 18:30 UTC. Credit: Stellarium

Another exciting thing happening in March, is that Saturn’s rings will disappear! Not literally, but on the 23^rd of March and a week either side, the rings will be at such an angle that we will barely see them from our point of view.

As Saturn orbits round the Sun every 29 years it tilts towards and away, meaning sometimes we see the planet edge on, and sometimes the rings open. The rings are only a few hundred meters thick and down to a few tens of meters in some places, which at 1.5 billion kilometres away is hardly anything at all.

When the rings vanish Saturn will be left looking like a pale yellow sphere through most telescopes. And only the most powerful telescopes will observe a subtle line through the planet’s middle.

And indeed, from most places on Earth it will be very difficult to get a good view of Saturn at all because it’s right next to the Sun. Hopefully our space telescopes will get a better view – having no atmosphere helps.

Image: Simulation of Saturn's rings and a few of its moons on the 23^rd of March. Credit: Stellarium

Special event: Eclipse Mania!

We have two eclipses for the price of one this month, how lucky!

The first on offer is a total lunar eclipse. On the 14^th of March the Sun, Earth and Moon will be perfectly lined up so that the Moon will be in the Earth’s shadow. Although most of the light from the Sun will be blocked, some light will pass through the Earth’s atmosphere and scatter, making the Moon appear very red. This is why a lunar eclipse is also called a “blood moon”.

The lunar eclipse will come at an inconvenient time for us folks in the UK, with the maximum happening at about 7am which 1) is very early, 2) will be quite light outside, but most importantly 3) will be below the horizon for us. For you early birds who still want to see some of it, I’d recommend getting up at about 5:30am on the 14^th to see the partial eclipse until it sets at about 6:30am.

It will still be quite light outside, and you’ll need to get a low westerly horizon, but hopefully you should still see some of it.

Image: Blood Moon. Credit: Kielder Observatory

The second is a partial Solar eclipse! This will be starting at about 10am UTC. It will only be partial but will be visible for 2 hours with the maximum partiality at 11am. When trying to look at it, please use solar filter glasses or a pin hole camera to project it onto the ground and DO NOT look at it with your naked eyes. 

Image: The partial solar eclipse on the 29th of March. Starting at 10:07 UTC, with the maximum at 11:05 UTC, finishing at 12:03 UTC. Credit: Pete Lawrence, The Sky at Night.

Phew! A lot of things to keep us all busy. That’s it for this month's What’s Up, happy stargazing!